#khung{
    width: 1000px;
    margin: auto;
    border: 1px solid #ccc;
    border-radius: 5px;
}
#dieukhien{
    width: 99%;
    padding:5px 0px;
    text-align: center;
    margin: 0.5%;
    background: #ccc;
}


root { 
    display: block;
}

